Exceptional morphological and taxonomic diversity of early seals (Phocidae) from the Atacama Region, Chile

Contrasting with their current ranges in the Antarctic and subantarctic zones, the fossil record reveals that phocids (true and elephant seals) inhabited widespread subtropical regions across the Southern Hemisphere in the geologic past. At least four extinct phocid taxa have been described from Miocene and Pliocene fossiliferous levels in Chile and Peru, constituting two of the taxonomically richest phocid assemblages known. Still, some Chilean remains morphologically differ from those recovered from Peru, suggesting an unprecedented phocid diversity. We examined phocid mandibular remains from the Bahia Inglesa Formation in northern Chile. We identified the occurrence of the long-snouted seal Acrophoca longirostris, a morphologically distinguishable and undescribed form of Acrophoca, and Hadrokirus martini, an extinct phocid with a robust feeding morphology, constituting the first record of this taxon outside Peru. We also recognised four other indeterminate phocids with considerable morphological differences from contemporaneous taxa. Moreover, one of these specimens uniquely combines morphological attributes distinct from all known extant and extinct phocids, likely corresponding to a new taxon. These reports significantly increase the taxonomic and morphological diversities of fossil seals from the eastern South Pacific and emphasise the substantial transformations of phocid assemblages over geologic time.